Malignant hydrothoracic refers to the phenomenon of abnormal increase of fluid in the body cavity due to diffuse lesions in the pleura of the thoracic cavity and abdominal cavity dirty wall layer caused by malignant tumors or carcinomatosis occurring in the whole body or thoracic and abdominal cavities. Malignant pleural and abdominal fluid is one of the complications of advanced cancer, and any patient with “pleural and abdominal fluid” indicates distant metastasis. Phosphorus 32 colloid is used to treat malignant hydrothorax by injecting phosphorus 32 colloid into the thoracic or abdominal cavity, where fluid has accumulated due to malignant tumors, and then allowing it to be diluted sufficiently and distributed evenly. It utilizes its radiated beta rays to radiate and kill the metastatic foci in the mucosa of the thoracic or abdominal cavity in order to reduce or temporarily stop the production of effusion and achieve the purpose of palliative treatment, with an effective rate of 80%. Phosphorus 32 colloid therapy is very effective and has few toxic side effects, providing more choices for the treatment of malignant pleural and abdominal fluid.